This invention relates to detection of mine roof movements and is an improvement over the movement monitoring apparatus disclosed in my prior U.S. Pat. No. 3,646,553, issued FEB. 2, 1972.
In the movement detecting apparatus of the type disclosed in my prior U.S. patent referred to, a sensing switch is mounted by a housing on the roof ceiling in operative relation to a switch actuator adjustably positioned on the lower end of the support bolt through which the switch housing is yieldably held in abutment with the roof ceiling. Sensitivity of the detecting apparatus depends, therefore, in large measure, on the mounting and operating characteristics of the sensing switch. Accordingly, the adjustment setting of the switch actuator is not always reliable and changes in sensitivity sometimes occurs even through no adjustment is made. Further, replacement of the sensing switch requires readjustment and is rather difficult without complete disassembly of the apparatus.
It is, therefore, an important object of the present invention to provide an improved movement detecting apparatus of the aforementioned type which includes a sensing switch that does not effect sensitivity adjustment and may be replaced without disturbing such adjustment.